This invention relates to a workpiece feeding apparatus and more particularly to an "inconstant-thickness" workpiece feeding apparatus for loading workpieces which have thicknesses which may vary.
A conventional inconstant-thickness workpiece feeding apparatus, as shown in FIG. 9, has been previously adapted to stack a plurality of workpieces such as shirt cuffs of various thicknesses whose hems or margins are seamed and then to pick up the workpieces one by one, therby being able to provide a continuous supply. In general, a box-shaped stacker 50 is adapted to receive therein a plurality of identical shirt cuffs 100 in a stack oriented in the same direction. The stacker 50 as well as the cuffs are raised by an elevating means (not shown) until the uppermost cuff reaches a predetermined elevation where it is then delivered to a well-known pickup unit 51 for use with a vacuum chuck or a hook. The pickup unit is then moved to feed the cuff to a next sewing station, such as a station including a buttonholing machine and a button sewing machine.
However, disadvantages derive from such conventional inconstant-thickness workpiece feeding apparatuses. For example, as shown in FIG. 10, cuffs 100 are generally formed in such a manner that a front fabric 102 and a back fabric 103 are overlapped, a lining strip is interposed therebetween and a fold is made along the three sides of the fabrics, thereby defining a hem 104. This will render folded portions 100a, 100b, and 100c thicker than the central portion.
Consequently, when a plurality of the identical cuffs are received in a stack oriented in the same direction in the stacker 50, the stack of cuffs sags on the side which does not have the hem so that the appearance of the stack is basically rectangular but with a curved portion. More specifically, the top of the stack provides a three dimensional curved surface with points a, b, c, and d in order of height as shown in FIG. 9. The greater the number of cuffs are, the more conspicuous this phenomenon becomes.
For this reason, it is very difficult for the pickup unit 51 to pick up the uppermost cuff since the latter is neither planar nor flat and its configuration with respect to the pickup unit varies and may not be stable depending upon material used in making the cuffs and the number of the cuffs in the stacker. This situation can make the apparatus function improperly.
Moreover, a conventional stacker 50 designed to accommodate a large plurality of the stacked cuffs would require massive and complicated equipment to control its elevation and height. This would also incur great expense.
It is therefore an object of the invention to provide an inconstant-thickness workpiece feeding apparatus capable of ensuring a supply of workpieces in a stable manner.
It is a further object of the invention to provide an inconstant-thickness workpiece feeding apparatus which is compact so as to make the apparatus inexpensive to manufacture.